In recent years, Ethernet (registered trademark) has been built as a low level protocol of an Internet Protocol (IP) network to connect a server in a company and a customer. Generally, Ethernet is made up of layer 3 switches or layer 2 switches that switch a packet based on media access control (MAC) address.
Ethernet also uses a link aggregation technique that handles multiple links as one virtual link to obtain broader bandwidth and redundant architecture. When packet quality degrades, a segment where a failure has occurred (hereinafter “faulty segment”) is detected accurately and the network is maintained.
The network tomography has been used to detect a faulty segment. According to the network tomography, a monitor is connected to a network to capture packets. The monitor captures packets and checks the quality of each packet. The monitor records segments through which a packet has passed with a routing protocol. The monitor creates a table that associates the quality of a packet with segments the packet has passes through. Based on the table, the monitor detects, as a faulty segment, a segment where the quality of a packet degrades (see, for example, Japanese Laid-open Patent Publication No. 2009-55113).
However, the above conventional technique cannot be applied to a case where multiple packets pass through the same path. Thus, the above conventional technique cannot detect a faulty segment from among segments on the path.